Milling of edible materials, such as grains and legumes, is a grinding and particle size reduction operation, generally designed to produce fine, uniform flour for comestible products. Milling separates the bran and germ from the generally more desirable endosperm portion of the grain. Semolina or semolina flour is the flour obtained from the milling of hard wheat such as the middlings of durum wheat. Semolina comprises a major portion of the milled flour in alimentary pastes because it is highly glutinous and produces a self supporting alimentary pasta.
It is known to treat pasta dough, or flour being made into pasta dough, with various modifiers, additives and agents for various purposes including color retention, improved nutritive value and greater pasta yield. For example, U.S. Pat. No. 3,762,931, issued Oct. 2, 1973 to Craig, et al. teaches the addition of edible sulfhydryl reducing substances to alimentary paste for the purposes of reducing moisture content, improving surface characteristics and decreasing drying time of the pasta. Known flour treatment agents include, for example, KBrO.sub.3, KIO.sub.3, azodicarbonamide (H.sub.2 NC(O)N.dbd.NC(O)NH.sub.2), chlorine dioxide, chlorine gas, benzoyl peroxide, ascorbic acid, and L-cysteine. Of these flour treatment agents, only ascorbic acid and 1-cysteine are reducing agents, while the remainder of the agents are oxidizing agents. To the knowledge of the inventors, reducing agents have not been used to treat edible grains and legumes in the tempering step prior to milling.
In "Durum Wheat: Chemistry and Technology", edited by G. Fabriani and C. Lintas, published by The American Association of Cereal Chemists, Inc., St. Paul, Minn., at pages 64-65, it is taught that the use of oxidation inhibitors, such as L-ascorbic acid, can inhibit the destruction of the yellow color in the processing of semolina.
In the commercial production of semolina, it is conventional to use chlorine gas in the tempering solution prior to milling of durum wheat. The chlorine gas is an oxidant and inhibits mold growth during shipping and storage of the flour produced. However, chlorine may be related to adverse effects on the quality of pasta products produced from the semolina. In addition, chlorine is a toxic gas and creates handling and venting problems in the tempering step.
It is also previously known to use sulfur dioxide as a bleaching agent in corn milling and/or in tempering of corn prior to milling for the purpose of reducing color content.
It is therefore an objective of the present invention to increase the yield of durum flour obtained from the milling of durum wheat by the addition of a reducing agent to the tempering step prior to milling.
It is also an object of the present invention to provide a method of improving color retention in milled edible grains and leguminous materials. It is a further object of the present invention to increase the nutritive value of durum flour in general and of semolina flour in particular obtained from the tempering and milling of durum wheat.